Power delivery systems typically transfer power to and from multiple locations. Such example systems are solar power delivery systems and automotive power processing systems. One example of a solar power delivery system would be the solar power delivery system utilized for home consumption. A photovoltaic (PV) cell converts the energy from received sunlight into electrical power. The power delivery system then transfers the electrical power to various locations around the home. Power may be transferred from a PV cell to a battery for power storage. In addition, power may be converted to the high voltage ac used for conventional wall sockets to power electronic devices. Typically, current systems use at least two independent devices which are used to transfer power in the solar power delivery system. One device, called a maximum power point tracker (MPPT), transfers power from a PV cell to a battery. The MPPT is a dc to dc power converter which extracts the optimum power from the PV cell. The solar power delivery system utilizes another device, a power inverter, which converts energy from the battery to the high voltage ac used for the power grid. A power inverter is a dc to ac power converter and is typically also a bidirectional power converter.
The power inverter may have multiple high voltage ac or dc outputs and inputs, each may have a different phase, amplitude, and/or frequency (50 Hz, 60 Hz, 100 Hz, single phase, slit-phase, or tri-phase) from the other. Internally, the power inverter utilizes one transformer for every high voltage isolated ac output. The MPPT mentioned above also internally utilizes an energy transfer element, such as an inductor or transformer. For a typical solar power delivery system having a PV cell, one battery and one high voltage ac output, two separate products each having their own transformer would be utilized. In addition, for every additional output of the power inverter, another transformer would be utilized. Two separate products add additional costs and result in greater size and weight to the power delivery system. Additional transformers also add additional cost, size, and weight to the power delivery system.
Others have attempted to combine the MPPT, multiple power inverters, or other power conversion systems into a single product with a single energy transfer element, such as a transformer, to reduce cost and size of the device. A power delivery system with a single energy transfer element which transfers energy to and from multiple locations is herein referred to as multiple power port conversion (MPPC). However, implementing MPPC for a power deliver system has many challenges and obstacles, namely, implementing the control loops for different locations connected to the single energy transfer element. For example, a MPPC system with 3 locations (also referred to as ports) transferring power between the first and second location would need to take into account the effects of the power transfer to the third location because the locations share a common path through the energy transfer element. As such, the control signal controlling power to or from the third location would offset the effects of the power transfer between the first and second location. The same can be said for power transfer between the first and third location and the effects to the second location. As such, the control techniques for each individual power port can become very complex when more power ports are connected to the energy transfer element. As such, the number of power ports which can be connected to the energy transfer element is limited due to the complex control loops generated for each port. Because of this, typical MPPC systems are limited to no more than three power ports.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.